Monkeys on Marijuana Wanted More

N E W Y O R K, Oct. 16, 2000

By Malcolm Ritter

A new federal study shows that monkeys will dose themselves with the
main active ingredient of marijuana repeatedly. Researchers say this evidence strengthens the theory that people can become addicted to pot and provides a new way to test therapies.

Lab animals will actively dose themselves with most drugs abused
by people, but marijuana has been an exception, said researcher
Steven Goldberg of the National Institute on Drug Abuse (NIDA).

Some people might interpret that as suggesting it has little
potential for addiction, he said. But the new work found that
squirrel monkeys repeatedly pushed a lever to get injections of the
marijuana ingredient THC, Goldberg and colleagues report in the
November issue of the journal Nature Neuroscience.

The animals pushed the lever about as much as other monkeys did
to get cocaine, but Goldberg said that does not necessarily mean
marijuana is as addictive as cocaine in people.

Causes Compulsive Craving

NIDA says marijuana causes compulsive and often uncontrollable
craving and use, despite health and social consequences, and therefore is
addictive.

The monkey study doesn’t prove otherwise, said Grinspoon, who is
chairman of the board of the NORML Foundation, which promotes
medical use of marijuana and, ultimately, its legalization.

In Goldberg’s experiment, four squirrel monkeys sat through
hour-long test sessions once a day with a tube attached to a vein.
When a green light turned on, they could push a lever 10 times to
get a THC injection.

They gave themselves up to 30 injections per session, versus one
to four when the tube delivered only water.

In proportion to their body size, the monkeys got about the same
dose of THC per injection that a person does with each puff from a
marijuana cigarette. The monkeys didn’t show any sign of being
sedated, Goldberg said.